Bilal said, "Messenger of Allah, do not say 'ameen' before me."
حدثنا محمد بن فضيل حدثنا عاصم
قال بلال يا رسول الله لا تسبقني بآمين
No references are available.
Its isnad is sahih. Abu Uthman Nahdi was a mukhadram successor who met Bilal. The hadith was narrated by Abu Dawud, 1/246, no. 937, and Bayhaqi, 2/56, both in the chapter on prayer.